[petsc-users] Using PETSc GPU backend

[Matthew Knepley]

On Fri, Jun 30, 2023 at 1:13 AM Ng, Cho-Kuen via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Mark,
>
> The application code reads in parameters from an input file, where we can
> put the PETSc runtime options. Then we pass the options to
> PetscInitialize(...). Does that sounds right?
>

PETSc will read command line argument automatically in PetscInitialize()
unless you shut it off.

  Thanks,

    Matt


> Cho
> ------------------------------
> *From:* Ng, Cho-Kuen <cho at slac.stanford.edu>
> *Sent:* Thursday, June 29, 2023 8:32 PM
> *To:* Mark Adams <mfadams at lbl.gov>
> *Cc:* petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
> *Subject:* Re: [petsc-users] Using PETSc GPU backend
>
> Mark,
>
> Thanks for the information. How do I put the runtime options for the
> executable, say, a.out, which does not have the provision to append
> arguments? Do I need to change the C++ main to read in the options?
>
> Cho
> ------------------------------
> *From:* Mark Adams <mfadams at lbl.gov>
> *Sent:* Thursday, June 29, 2023 5:55 PM
> *To:* Ng, Cho-Kuen <cho at slac.stanford.edu>
> *Cc:* petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
> *Subject:* Re: [petsc-users] Using PETSc GPU backend
>
> Run with options: -mat_type aijcusparse -vec_type cuda -log_view
> -options_left
>
> The last column of the performance data (from -log_view) will be the
> percent flops on the GPU. Check that that is > 0.
>
> The end of the output will list the options that were used and options
> that were _not_ used (if any). Check that there are no options left.
>
> Mark
>
> On Thu, Jun 29, 2023 at 7:50 PM Ng, Cho-Kuen via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
> I installed PETSc on Perlmutter using "spack install petsc+cuda+zoltan" and
> used it by "spack load petsc/fwge6pf". Then I compiled the application
> code (purely CPU code) linking to the petsc package, hoping that I can get
> performance improvement using the petsc GPU backend. However, the timing
> was the same using the same number of MPI tasks with and without GPU
> accelerators. Have I missed something in the process, for example, setting
> up PETSc options at runtime to use the GPU backend?
>
> Thanks,
> Cho
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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